Flexible unbonded pipe and a method for producing such pipe

ABSTRACT

The present invention relates to a flexible unbonded pipe comprising an inner liner capable of forming a barrier against outflow of a fluid which is conveyed through the pipe, and one or more armouring layers on the outer side of the inner line. The flexible unbonded pipe comprises at least one polymer layer and one film layer, said polymer layer being bonded to said film layer. The film layer may preferably be a metal film layer, such as aluminum film, stainless steel film or duplex film. The polymer layer may preferably be cross-linked polyethylene. The interfacial bonding between the polymer layer and the film layer should preferably be sufficiently strong to prevent creation of gas pockets between the layers when subjected to an increased pressure of aggressive fluids (hydrogen, sulphides, methane and carbon dioxide) on the film side of the pipe. Thereby, it is possible to protect armour layer(s) from aggressive fluids.

This application claims priority benefits based on Danish PatentApplication No. PA 2003 01371, Filed Sep. 19, 2003, and is a NationalPhase Application of PCT/DK2004/000637PCT.

TECHNICAL FIELD

The present invention relates to a flexible unbonded pipe and a processfor its preparation. The flexible unbonded pipe is particularly usefulin aggressive environments, due to its ability to withstand thediffusion of gases from a fluid in the pipe.

BACKGROUND ART

Flexible unbonded pipes as such are well known in the art. Such pipescomprise an inner liner which forms a barrier against the outflow of thefluid which is conveyed through the pipe, and one or more armouringlayers on the outer side of the inner liner (Outer armouring layer(s)).The flexible pipe may comprise additional layers such as one or moreinner armour layers to prevent the collapse of the inner liner. Suchinner armouring layer or layers are normally referred to as a carcass.An outer sheath may be provided with the object of forming a barrieragainst the ingress of fluids from the pipe surroundings to the armourlayers.

Typical unbonded flexible pipes are e.g. disclosed in WO0161232A1, U.S.Pat. No. 6,123,114 and U.S. Pat. No. 6,085,799.

The term “unbonded” means in this text that at least two of the layersincluding the armouring layers and polymer layers are not bonded to eachother. In practice the pipe will comprise at least two armouring layers,which are not bonded to each other directly or indirectly via otherlayers along the pipe. Thereby the pipe becomes bendable andsufficiently flexible to roll up for transportation.

The above-mentioned type of flexible pipes is used, among other things,for off shore as well as some on-shore applications for the transport offluids and gases. Flexible pipes can e.g. be used for the transportationof fluids where very high or varying water pressure exists along thelongitudinal axis of the pipe, such as riser pipes which extend from theseabed up to an installation on or near the surface of the sea, pipesfor transportation of liquid and gases between installations, pipeswhich are located at great depths on the seabed, or betweeninstallations near the surface of the sea.

In traditional flexible pipes, the one or more outer armouring layersare most often in the form of helically wound steel wires e.g. shaped asprofiles, where the individual layers may be wound at different windingangle relative to the pipe axis.

When using such prior art flexible pipes for transportation ofaggressive gases, raw oils and similar fluids, it has been found thatundesired and often corrosive gases and liquids are diffusing throughthe inner liner and into the outer armouring layers.

In prior art pipes, this problem has been solved in a number ofdifferent ways. In EP 1119684 a solution is disclosed where the lumenbetween an inner liner and an outer sheath can be flushed to removeundesired gases and liquids that has been diffusing through the innerliner into the lumen. This solution is however not suitable in allsituations.

Another approach for preventing the aggressive and destructive corrosionof the armour wires is to provide armour wires of a non-corrosivematerial. Such solution has been disclosed in WO 02095281, wherein thearmouring wires are made from a composite material. Such wires arehowever relatively expensive.

In WO0231394 it is suggested to allow environmental sea water to comeinto contact with the outer armour layers whereby gases and liquids thathave been diffusing through the inner liner are flushed away from thearmours. As the sea water may be corrosive in itself, this solutioneither requires that the armour wires are of a non-corrosive material orthat the pipe is used in low corrosive outer environments.

U.S. Pat. No. 6,006,788 discloses a flexible pipe with an internal gasproof undulating metal tube. However, this pipe is relatively stiff asthe internal gas proof undulating metal tube needs to have a certainthickness in order to be sufficiently stable. Furthermore, the internalgas proof metal tube need to be resistive to the medium to betransported in the pipe, which in practice means that pipes of this typehave a very limited used.

SUMMARY OF INVENTION

The objective of the invention is to provide a flexible, unbonded pipeuseful for transportation of gases and crude oils and other aggressivefluids, which pipe is improved compared with the respective prior artpipes. In particular, it is an objective to provide a flexible, unbondedpipe which does not have the drawbacks of the prior art pipes describedabove.

The invention also aims at providing a method for producing suchflexible, unbonded pipes.

These objectives have been solved by the invention as it is defined inthe claims and described in the following.

The flexible pipe according to the invention can thus be used fortransporting corrosive gases, crude oils and other corrosive fluids,with less tendency for corrosion of the armouring wires than prior artsolutions as disclosed above.

Simultaneously, the construction is very simple and easy to produce, andfurthermore the corrosion stability properties obtained are not at theexpense of flexibility properties of the flexible pipe.

According to the invention the flexible pipe according to the inventionhas an increased corrosion stability due to the fact that the diffusionof aggressive fluids into the armouring wires is reduced or eveneliminated while the flexible pipe remains sufficiently flexible forbeing transported on reels.

DISCLOSURE OF INVENTION

The flexible pipe according to the invention thus comprises at least onepolymer layer and one film layer, said polymer layer being bonded tosaid film layer.

Generally, it is desired that the film layer is thinner than saidpolymer layer, and that said film layer furthermore provides a higherdiffusion barrier to the fluids in question, i.e. the gasses or liquidsto be transported in the pipe.

The polymer layer may in principle be any kind of polymer layer.

In one embodiment, it is desired that the polymer layer is capable ofresisting the high temperatures of the fluid conveyed e.g. in the orderof 130° C. to 150° C., or even in the order of 130° C. to 180° C., andwhich is easy to work industrially, in particular by extrusion. Thepolymeric materials that have these properties include in particularcertain semi-crystalline polymers. Furthermore, it is desired that thepolymer layer should be resistant to live crude with little or noblistering or swelling.

Examples of useful polymers for the polymer layers include thefollowing:

polyolefins, such as polyethylene and poly propylene;

polyamide, such as poly amide-imide, polyamide-11 (PA-11) andpolyamide-12 (PA-12);

polyimide (PI);

polyurethanes;

polyureas;

polyesters;

polyacetals;

polyethers, such as polyether sulphone (PES);

polyoxides;

polysulfides, such as polyphenylene sulphide (PPS);

polysulphones, such as polyarylsulphone (PAS);

polyacrylates;

polyethylene terephthalate (PET);

polyether-ether-ketones (PEEK);

polyvinyls;

polyacrylonitrils;

polyetherketoneketone (PEKK); and co-polymers of the preceding;

fluorous polymers such as polyvinylidene diflouride (PVDF), homopolymersand copolymers of vinylidene fluoride (“VF2”), homopolymers andcopolymers of trifluoroethylene (“VF3”), copolymers and terpolymerscomprising two or more different members selected from the groupconsisting of VF2, VF3, chlorotrifluoroethylene, tetrafluoroethylene,hexafluoropropene, and hexafluoroethylene.

The flexible pipe of the invention may thus preferably comprise at least50% by weight, such as at least 70% by weight, such as at least 85% byweight of one or more of the polymers selected from the group ofpolymers specified.

In one embodiment, the polymer layer comprises one or more of polyamide,poly(vinylidene fluoride) (PVDF).

In one embodiment, the polymer layer comprises at least 50% by weight,such as at least 85% by weight of cross-linked polyethylene (XLPE). Inone embodiment, the polymer layer consisting essentially of cross-linkedpolyethylene (XLPE) and one or more inorganic fillers.

The polymer layer may preferably be as in the co-pending applicationPCT/DK 03/00191, which is cross-linked using IR radiation. Thedisclosure of PCT/DK 03/00191 is hereby incorporated by reference.

The film layer may in principle be a film of any type of material which,preferably in the desired thickness e.g. less than 2 mm or even lessthan 1 mm, is flexible.

Useful film layers include materials of the group consisting of polymer,metal, metal containing compositions and combinations thereof.

Useful polymer materials for the film include inter alia polymer filmcomprising one or more of the polymer material selected from the groupconsisting of

polyolefins, such as polyethylene and poly propylene;

polyamide, such as poly amide-imide, polyamide-11 (PA-11), polyamide-12(PA-12) and polyamide-6 (PA-6);

polyimide (PI);

polyurethanes;

polyureas;

polyesters;

polyacetals;

polyethers, such as polyether sulphone (PES);

polyoxides;

polysulfides, such as polyphenylene sulphide (PPS);

polysulphones, such as polyarylsulphone (PAS);

polyacrylates;

polyethylene terephthalate (PET);

polyether-ether-ketones (PEEK);

polyvinyls;

polyacrylonitrils;

polyetherketoneketone (PEKK); and lymers of the preceding;

fluorous polymers such as polyvinylidene diflouride (PVDF), homopolymersand copolymers of vinylidene fluoride (“VF2”), homopolymers andcopolymers of trifluoroethylene (“VF3”), copolymers and terpolymerscomprising two or more different members selected from the groupconsisting of VF2, VF3, chlorotrifluoroethylene, tetrafluoroethylene,hexafluoropropene, and hexafluoroethylene.

In one embodiment, the film layer is made from metal e.g. in the form ofa metal film such as a film comprising or consisting of aluminum,stainless steel and/or duplex.

In one embodiment, the film layer is a layered material. The layeredfilm may e.g. be composed of a metal layer and a primer layer, whereinthe primer preferably may be a layer comprising C atoms. This aspectwill be described further below.

In one embodiment, the layered film comprises at least one metal layer,such as two, such as three metal layers. The film layer may optionallycomprise one or more polymeric layers.

In one embodiment, the film layer may comprise metal containingcompositions, such as metal oxides and metal halides. When using suchmaterial the film layer should preferably be a layered material so thatthe metal oxides and metal halides are protected from contact withcorrosive fluids.

The film layer may in one embodiment be a mixture of polymer with carbonand/or metal and/or metal containing particles.

In order to minimize the risk of forming gas pockets in the interfacialarea of the combined polymer layer and film layer, these layers arebonded to each other. The bonding may in principle be provided by anymeans provided it is sufficiently strong to avoid the creation ofinterfacial gas pockets.

In one embodiment, the polymer layer is bonded to the film layer via oneor more bondings from the group of physical bondings and chemicalbondings, such as ion bondings and covalent bondings.

In one embodiment, it is desired that the bonding between the polymerlayer and the film layer is stronger than the internal bondings in oneof the polymer layer and the film layer.

This property may be measured by a peel test for tearing the film andthe polymer layer from each other. e.g. using ASTM D3330.

When performing the peel test it is in one embodiment desired that thebonding between the polymer layer and the film layer is so strong thatthe combined film/tape is not only separated along its interfaciallayers, but that the material of at least one of the layers is torn up,or in other words that at least one of the layers has cohesion failureunder the load applied during the peel test.

In one embodiment, the combined film/tape has a peel strength using ASTMD3330 of at least 300 N/m, such as at least 500 N/m, such as at least700 N/m.

In one embodiment, where the film layer in itself is a layered material,e.g. of two, three or four individual polymer, metal or other layers,all interface bondings including bondings between layers of the film andbondings between the polymer layer and the film layer, are stronger thanthe internal bondings in one of the polymer layer and the film layer.The individual layers may e.g. be glued or pressed together, or thebonding may be obtained by subjecting the polymeric layer to heat tosoftening or even melting point. As another alternative the individuallayers may be sprayed or brushed e.g. in the form of a solution ordispersion in a solvent, which solvent afterwards is allowed toevaporate.

In one embodiment, the interface bondings(s) between the one or morelayers is/are stronger than the internal bonding of the polymer layer.

In one embodiment, the interfacial bonding between the polymer layer andthe film layer is sufficiently strong to prevent creation of gas pocketsbetween the layers when subjected to an increased carbon dioxidespressure on the film side of the pipe, the increased carbon dioxidespartial pressure e.g. being 1 bar, 5 bars 10, bars or even 50 bars.

The bonding between the polymer layer and the film layer may e.g. besufficiently strong to prevent creation of gas pockets between thelayers when subjected to an increased pressure on the film side of thepipe, where the pressure is 5 bar, 10 bars 50, bars or even 100 bars orhigher, and where the gas comprises at least 10% by vol. of methane, atleast 10% by vol. of hydrogen sulphides, and at least 10% by vol. ofcarbon dioxides.

In one embodiment, it is desired that the film layer or at least thesurface of the film that is facing the polymer layer comprises C atoms.Thereby an improved adhesion between the film layer and the polymerlayer may be obtained, in particular if the polymer layer is subjectedto a cross-linking step after being applied face to face with the filmlayer, because this cross-linking step may provide covalent bondingsbetween the polymer layer and the C atoms of the film layer.

In one embodiment, the surface of the film facing the polymer layercomprises a primer. This primer may in principle be any type of primerthat facilitates a satisfactory bonding between the polymer layer andthe film layer. The primer may e.g. be a C atom containing primer.

Thus, in one embodiment the film or the film with a primer comprises Catoms, and the polymer is a cross-linked polymer with bondings linkingto the C atoms of the film.

The optimal primer depends largely on the film layer material. Examplesof useful primers include latex primers (UCAR™ Latex by DOW. Latex MetalPrimer—DTM by Hytech), epoxy primers (EP420 PRIMER GREEN by AEROCENTERAIRCRAFT SUPPLY and AVIONICS), ascrylat/methacrylat primers, Rusty MetalPrimer by Rustoleum, Metal-Prime by Hytech, Anti-rust primer by PlasconInternational Ltd, MPI #23 Surface Tolerant Metal Primer by Bennettepaint.

The primer may for example be applied by spraying gluing and/orpressing. Alternatively the primer may be a plasma deposited layer.

The thickness of the polymer layer should preferably be in the intervalof 4 to 25 mm. A too thin layer may have too low mechanical strength,whereas a too thick polymer layer may result in reduced flexibility ofthe final unbonded pipe. In general, it is thus desired that the polymerlayer has a thickness of at least 4 mm, such as at least 6 mm, such asat least 8 mm, such as at least 10 mm, such as at least 12 mm, andpreferably the polymer layer has a thickness between 4 and 20 mm, suchas between 8 and 15 mm.

For maintaining high flexibility while having low gas permeability, itis desired that the polymer layer is thicker than the film layer, suchas 4 times as thick or more, such as 10 times as thick or more such as10 times as thick or more, such as 50 times as thick or more, such as upto 100 times as thick.

Desired thickness of the film layer is therefore in general less than 4mm. The film layer may thus e.g. have a thickness of about 25 μm ormore, such as about 100 μm or more, such as about 500 μm or more, suchas about 1 mm or less.

In one embodiment, the film is in the form of a tape wound onto thepipe, where the term “tape” includes thin films of 1 mm or less and witha width of up to 10 cm.

As indicated above, it is desired that the major gas barrier is providedwith the film layer. In one embodiment, the film layer is the innermostlayer of said film layer and said polymer layer. Since the film layerhas a low or no gas permeability to the gases methane, hydrogensulphides, carbon dioxides, the polymer layer is protected from thesegases and the requirements to the chemically stability of the polymerlayer is low compared with prior art polymer inner liners.

By having a high barrier against the aggressive gases in the innermostlayer which is thereby in direct contact with the fluid to betransported in the pipe, focus can be put on other properties whenchoosing the material for the polymer layer.

In an alternative embodiment, the polymer layer is the innermost layerwhich is thereby in direct contact with the fluid to be transported inthe pipe. The film layer is thus partly protected from the aggressivefluids to be transported in the pipe. In this embodiment, in order tohave an acceptable lifetime the polymer layer should preferably have ahigh chemically resistance.

The film layer preferably has a higher diffusion barrier to methane,hydrogen sulphides, carbon dioxides and water than the polymer layer.

In one embodiment, the film layer provides a fluid permeation barrieragainst one or more and preferably all of the fluids methane, hydrogensulphides, carbon dioxides and water, which is higher, such as least 50%higher, such as least 100% higher, such as least 500% higher, such asleast 1000% higher, than the fluid permeation barrier provided by thepolymer layer determined at 50° C. and a pressure difference of 50 bar.

In one embodiment, the film layer is essentially impermeable to one ormore of the fluids hydrogen sulphides, methane and carbon dioxide, at apartial pressure for the respective fluids on the first side of thelayer of 0.03 bars or more, such as 0.1 bars or more, such as 1 bar ormore, such as 10 bars or more measured at about 50° C. and a pressuredifference of 50 bar.

In one embodiment, the film layer is essentially impermeable to H2O(preferably liquid or gas), and a pressure difference of 50 bar.

In one embodiment, the film layer is essentially impermeable to hydrogensulphides at a partial pressure of 0.03 bars or more, such as 0.1 barsor more at a temperature of about 25° C., preferably at a temperature ofabout 50° C., preferably at a temperature of about 90° C., preferably ata temperature of up to about 150° C. and a pressure difference of 50bar.

In one embodiment, the film layer is essentially impermeable to methaneat a partial pressure of 1 bar or more, such as 10 bars or more at atemperature of about 25° C., preferably at a temperature of about 50°C., preferably at a temperature of about 90° C., preferably at atemperature of up to about 150° C. and a pressure difference of 50 bar.

In one embodiment, the film layer is essentially impermeable to carbondioxide, at a partial pressure of 1 bar or more, such as 10 bars or moreat a temperature of about 25° C., preferably at a temperature of about50° C., preferably at a temperature of about 90° C., preferably at atemperature of up to about 150° C. and a pressure difference of 50 bar.

In one embodiment, the film layer is sandwiched between two polymerlayers. It is in this embodiment desired that at least one of thepolymer layers is bonded to the film layer with a bonding that isstronger than the internal cohesion of said polymer layer.

At least one of the polymer layers in the sandwich structure andpreferably both, independently of each other, are of a polymer selectedfrom the group as specified above.

In one sandwich structure embodiment, the innermost polymer layer of thetwo polymer layers is PVDF and the polymer layer on the in radialdirection outermost of the two polymer layer is cross-linkedpolyethylene (XLPE). In another alternative embodiment, the innermostpolymer layer of the two polymer layers is cross-linked polyethylene(XLPE).

The tape may e.g. be a wound or folded tape, e.g. wound or foldeddirectly on a carcass or wound or folded onto an innermost polymerlayer.

The flexible unbonded pipe may e.g. comprise one or more innermostunbonded armouring layers normally referred to as a carcass. Suchcarcass is preferably a metallic carcass and is normally fluid pervious.In one embodiment, the carcass is of wound interlocked profiles.

The flexible unbonded pipe of the invention comprises an inner linerwhich forms a barrier against the outflow of the fluid which is conveyedthrough the pipe, and one or more armouring layers on the outer side ofthe inner liner (Outer armouring layer(s)). The flexible pipe maycomprise additional layers such as one or more inner armour layers toprevent the collapse of the inner liner. Such inner armouring layer orlayers are normally referred to as a carcass. An outer sheath may beprovided with the object of forming a barrier against the ingress offluids from the pipe surroundings to the armour layers cover layer andone or more intermediate layers. At least one of said inner liners,intermediate layers and outer sheath is in the form of a combinedpolymer/film layer as described above.

The armour layers on the outer side of the inner liner may e.g. be of acomposite material e.g. as disclosed in WO 02095281. Alternatively thearmour layers may be of metal profiles helically wound e.g. as disclosedin WO 0036324 and WO0181809.

In one embodiment, the flexible tubular pipe of the invention comprisesat least one inner liner in the form of a combined polymer/film layer asdescribed above and at least one armouring layer which is not bonded tothe combined polymer/film layer.

In one embodiment, the pipe is of the type comprising at least, from theinterior towards the exterior, an internal non-impervious metal carcass,an inner liner, a set of layers of reinforcement wires, and an externalprotection sheath, at least one of said inner liners, intermediatelayers and outer sheath being in the form of a combined polymer/filmlayer as described above.

The one or more outer armouring layers may preferably be in the form ofhelically wound steel wires e.g. shaped as profiles, where theindividual layers may be wound at different winding angle relative tothe pipe axis.

In one embodiment, the flexible pipe comprises, from the inside to theoutside, a body consisting of an interlocked steel tape, an inner linerin the form of a combined polymer/film layer as described above, atleast one pressure armouring consisting of interlocked wires spirallywound with a small pitch (e.g. a winding at an angle in relation to theaxis of the pipe of about 85°), at least one layer of traction armourwires spirally wound with a long pitch (e.g. a winding at an angle inrelation to the axis of the pipe of about 35°). This configuration isreferred to as rough bore.

In another embodiment, the flexible pipe comprises an inner liner in theform of a combined polymer/film layer as described above, a firstarmouring mainly withstanding the pressure generated by the fluid in theinternal sheath, generally referred to as pressure layer, possibly asecond armour essentially withstanding the traction produced notably bythe pressure of the fluid. This variant is referred to as smooth bore.

In a further embodiment, the flexible pipe comprises an inner liner inthe form of a combined polymer/film layer as described above, anarmouring (outer armouring) placed above the inner liner, bothwithstanding longitudinal tensile stresses and the circumferentialcomponent due to the inside pressure of the fluid. Such a pressurearmouring can comprise two layers of reverse-pitch spiral wires whosearmouring angles are close to 55° in relation to the axis of the pipe.The stresses due to the inside pressure are in this case taken up bythese layers.

The invention also relates to a method of producing a flexible unbondedpipe comprising the steps of providing at least one polymer layer and atleast one film layer and bonding said layers to each other.

The layers polymer layer and film layer may be bonded as disclosedabove.

The method according to the invention preferably comprises the steps of

-   -   providing an innermost polymer layer, preferably around a        mandrel or an inner armour layer (carcass), more preferably by        extrusion, winding or wrapping,    -   providing a film layer around said innermost polymer layer,        preferably by extrusion, winding or wrapping,    -   providing a second polymer layer around said film layer,        preferably by extrusion, and    -   providing a bonding between at least one of said polymer layers        and said film layer, said bonding preferably being provided by        subjecting said at least one polymer layer to cross-linking.

In this method a sandwich structure as disclosed above is produced.

In a variation thereof, the method according to the invention comprisesthe steps of

-   -   providing a film layer around a mandrel or an inner armour layer        (carcass), preferably by extrusion, winding or wrapping,    -   providing a polymer layer around said film layer, preferably by        extrusion, and    -   providing a bonding between said polymer layers and the film,        said bonding preferably being provided by cross-linking of the        polymer layer.

In yet another variation thereof, the method according to the inventioncomprises the steps of

-   -   providing the innermost layered section of the flexible pipe        comprising at least an innermost polymer layer and an armour        layer on the outer side of said innermost polymer layer,    -   providing a film layer around said innermost layered section of        the flexible pipe, preferably by extrusion, winding or wrapping,    -   providing an outer polymer layer around said film layer,        preferably by extrusion, and    -   providing a bonding between at least one of said polymer layers        and the film, said bonding preferably being provided by        subjecting said polymer layer to cross-linking.

The film may be as disclosed above. In one embodiment, it is desiredthat the film e.g. the metallic film is treated by corona or byapplication of a primer for increasing bonding, said primer preferablybeing applied using CVD, spraying, dipping and/or rolling. Thereby animproved adhesion between the polymer layer and the film layer can beobtained.

For additional adhesion it is desired that the film or a primer coatedonto said film comprises C atoms, thereby covalent bondings can beprovided when subjecting the polymer layer to cross-linking.

The primer may be as disclosed above.

The polymer layer to be cross-linked may preferably be as in the copending application PCT/DK 03/00191, and may therefore preferably besubjected to cross-linking using IR radiation.

In one embodiment, it is thus desired that at least one polymer layer iscross-linked after being applied in contact with the film, which filmpreferably comprises C-atoms.

EXAMPLES Example 1

A self-interlocking carcass of 6″ inner diameter (15.2 cm) is produced.The outer diameter of this steel carcass is approximately 16.7 cm. Ontothe carcass a tape consisting of a 0.1 mm thick steel coated with anacrylat/methacrylat primer is wound. The tape has a width of 5 cm and iswound with an overlap of about 4 mm.

Onto the tape a polymer layer in the form of a polyethylene is extruded.The carcass with tape is fed into the centre of a crosshead tool. Inthis tool, the polyethylene melt is distributed in a pipe type tool andupon the exit of the crosshead is drawn onto the carcass with tape inapprox. 6 mm thickness at a line speed of 0.48 to 0.55 meters/minute.

The extruder is a conventional polyethylene single screw extruder with a120 mm screw diameter and an L/D ratio of 30, with a standard screw. Theextrusion process is found not to be temperature sensitive. Thetemperature setting on the heating zones of the extruder and head rangesfrom 150 to 165° C., and melt temperature is typically 160° C.

The polyethylene is a mixture of 90% HD-PE, grade 5621 from Basell and10% UHW-PE powder, grade HE 2591 from Borealis. The additives are amixture of 0.45% DYBP from Degussa and 0.40% Irganox XP621 from Ciba.DYBP (2,5-dimethyl hexine-3 2,5-di-t-butyl peroxide) is the peroxidewhich induces cross-linking of the PE. DYBP is activated by infraredradiation (DYBP may also be activated by heat at 180° C., thus thetemperature in the extruder should not at any time exceed 175° C.).Irganox is an antioxidant. The material is fed into the extruder as apremix.

After the extrusion the pipe passes through an IR oven with a capacityof 75 kW. Residence-time in the oven is 30-60 seconds.

After this the carcass with inner liner is cooled with water and ledthrough a caterpillar.

Thereafter a pressure armouring consisting of interlocked wires wasspirally wound with a small pitch and a traction armour wire spirallywound with a long pitch, and finally the pipe was coated with an outersheet provided by extrusion.

Example 2

A pipe is produced as in example 1 with the difference that a film asdisclosed in example 1 is provided onto the traction armour wires andthat the outer sheath is a 6 mm polyethylene as disclosed in example 1and that the polyethylene of the outer sheath is subjected to anirradiation after the extrusion thereof.

Example 3

A pipe is produced as in example 1 with the difference that a polymerlayer of PVDF is applied by extrusion directly onto the carcass and thatthe film is wound onto the PVDF layer.

1. A flexible unbonded pipe, said pipe comprising at least one polymerlayer having a thickness of 4 mm or more, least one film layer having athickness of greater than 0 mm and 1 mm or less, and one or morearmouring layers, said polymer layer being at least 10 times as thick asthe film, said film layer providing a fluid permeation barrier againstone or more of the fluids methane, hydrogen sulphides, carbon dioxidesand water, which is higher than the fluid permeation barrier provided bythe polymer layer determined at 50° C. and a pressure difference of 50bar, and said polymer layer being bonded to said film layer via one ormore bondings selected from the group of chemical bondings and physicalbondings, wherein said armouring layers are not bonded to said polymerlayer, and said armouring layers are not bonded to each other, andwherein said film layer and said polymer layer are of differentmaterials.
 2. A flexible pipe according to claim 1 wherein the polymerlayer comprises one or more of the polymers selected from the groupconsisting of polyolefins; polyamide; polyimide (PI); polyurethanes;polyureas; polyesters; polyacetals; polyethers; polyoxides;polysulfides; polysulphones; polyacrylates; polyethylene terephthalate(PET); polyether-ether-ketones (PEEK); polyvinyls; polyacrylonitrils;polyetherketoneketone (PEKK); copolymers of the preceding and fluorouspolymers.
 3. A flexible pipe according to claim 2 wherein the polymerlayer comprises cross-linked polyethylene (XLPE).
 4. A flexible pipeaccording to claim 1 wherein the film layer is of a material selectedfrom the group consisting of polymer, metal, metal containingcompositions and combinations thereof.
 5. A flexible pipe according toclaim 4 wherein the film layer is a polymer film comprising one or moreof the polymer material selected from the group consisting ofpolyolefins; polyamide; polyimide (PI); polyurethanes; polyureas;polyesters; polyacetals; polyethers; polyoxides; polysulfides;polysulphones; polyacrylates; polyethylene terephthalate (PET);polyether-ether-ketones (PEEK); polyvinyls; polyacrylonitrils;polyetherketoneketone (PEKK); copolymers of the preceding and fluorouspolymers.
 6. A flexible pipe according to claim 4 wherein the film layeris a metal film selected from the group consisting of aluminum,stainless steel and duplex.
 7. A flexible offshore pipe according toclaim 4 wherein the film layer is a layered material comprising at leastone metal layer.
 8. A flexible pipe according to claim wherein the filmlayer comprises metal-containing compositions.
 9. A flexible pipeaccording to claim 4 wherein the film layer comprises a mixture ofpolymer with particles selected from the group consisting of carbonparticles, metal particles, metal-containing particles, and mixturesthereof.
 10. A flexible pipe according to claim 1 wherein the polymerlayer is bonded to the film layer via one or more bondings comprising atleast one of the chemical bondings selected from the group of ionbondings and covalent bondings.
 11. A flexible pipe according to claim 1wherein the bonding between the polymer layer and the film layer isstronger than the internal bondings in one of the polymer layer and thefilm layer.
 12. A flexible pipe according to claim 11 wherein the filmlayer is a layered material, and all interface bondings includingbondings between layers of the film and bonding between the polymerlayer and the film layer, are stronger than the internal bondings in oneof the polymer layer and the film layer.
 13. A flexible pipe accordingto claim 11 wherein, the interface bonding(s) is/are stronger than theinternal bonding of the polymer layer.
 14. A flexible pipe according toclaim 1 wherein the interfacial bonding between the polymer layer andthe film layer is sufficiently strong to prevent creation of gas pocketsbetween the layers when subjected to an increased carbon dioxidespressure on the film side of the pipe.
 15. A flexible pipe according toclaim 1 wherein the bonding between the polymer layer and the film layerhas a peel strength using ASTM D3330 of at least 300 N/m.
 16. A flexiblepipe according to claim 1 wherein the bonding between the polymer layerand the film layer is stronger than the cohesive forces in one of thepolymer layer and the film layer measured by 90° peel test.
 17. Aflexible pipe according to claim 1 wherein the surface of the filmfacing the polymer layer comprises a primer.
 18. A flexible pipeaccording to claim 1 wherein the polymer layer has a thickness between 4and 20 mm.
 19. A flexible pipe according to claim 1 wherein the filmlayer has a thickness of about 25 μm or more and 1 mm or less.
 20. Aflexible pipe according to claim 1 wherein the film layer provides afluid permeation barrier against at least one of the fluids selectedfrom methane, hydrogen sulphides, carbon dioxides and water, which is atleast 50% higher than the fluid permeation barrier provided by thepolymer layer determined at 50° C. and a pressure difference of 50 bar.21. A flexible pipe according to claim 1 wherein the film layer providesa fluid permeation barrier against all of the fluids methane, hydrogensulphides, carbon dioxides and water, which is higher than the fluidpermeation barrier provided by the polymer layer determined at 50° C.and a pressure difference of 50 bar.
 22. A flexible pipe according toclaim 20 wherein the film layer is essentially impermeable to at leastone of the fluids selected from hydrogen sulfides, methane, and carbondioxide, at a partial pressure for the respective fluid on a first sideof the layer of at least 0.03 bars measured at about 50° C. and apressure difference of 50 bar.
 23. A flexible pipe according to claim 20wherein the film layer is essentially impermeable to H₂O, measured atabout 50° C. and a pressure difference of 50 bar.
 24. A flexible pipeaccording to claim 20 wherein the film layer is essentially impermeableto hydrogen sulfides at a partial pressure of at least 0.03 bars at atemperature of about 25° C. and a pressure difference of 50 bar.
 25. Aflexible pipe according to claim 20 wherein the film layer isessentially impermeable to methane at a partial pressure of at least 1bar at a temperature of about 25° C. and a pressure difference of 50bar.
 26. A flexible pipe according to claim 20 wherein the film layer isessentially impermeable to carbon dioxide, at a partial pressure of atleast 1 bar at a temperature of about 25° C. and a pressure differenceof 50 bar.
 27. A flexible pipe according to claim 1 wherein said filmlayer is the innermost layer of said film layer and said polymer layer.28. A flexible pipe according to claim 1 wherein said film layer issandwiched between two polymer layers, at least one of the polymerlayers being bonded to the film layer, with a bonding that is strongerthan the internal cohesion of said polymer layer.
 29. A flexible pipeaccording to claim 1 wherein said film layer is sandwiched between twopolymer layers, and the innermost polymer layer of the two polymerlayers is selected from the group consisting of polyolefins; polyamide;polyimide (PI); polyurethanes; polyureas; polyesters; polyacetals;polyethers; polyoxides; polysulfides; polysulphones; polyacrylates;polyethylene terephthalate (PET); polyether-ether-ketones (PEEK);polyvinyls; polyacrylonitrils; polyetherketoneketone (PEKK); copolymersof the preceding and fluorous polymers.
 30. A flexible pipe according toclaim 29 wherein the innermost polymer layer of the two polymer layersbeing PVDF (poly(vinylidene fluoride)) and the polymer layer on the inradial direction outermost of the two polymer layer is cross-linkedpolyethylene (XLPE).
 31. A flexible pipe according to claim 29 whereinthe innermost polymer layer of the two polymer layers is cross-linkedpolyethylene (XLPE).
 32. A flexible pipe according to claim 1 whereinthe film layer is in the form of a tape wound around an innermostpolymer layer.
 33. A flexible pipe according to claim 1 wherein the filmlayer is in the form of a tape folded around an innermost polymer layer.34. A flexible pipe according to claim 1 wherein said film layercomprises C atoms, the polymer being a cross-linked polymer withbondings linking to the C atoms of the film layer.
 35. A flexible pipeaccording to claim 1 wherein said pipe comprises one or more innermostunbonded armouring layers (carcass).
 36. A flexible pipe according toclaim 1 wherein at least one of said armouring layers is on the outerside of the polymer layer bonded to said film layer.